High purity water is required for many industrial applications including microelectronics manufacturing, all types of boiler feed, humidification, pharmaceutical manufacturing, and more. The United States Pharmacopeia (“USP”) is the official public standards-setting authority for all prescription and over-the-counter medicines, dietary supplements, and other healthcare products manufactured and sold in the United States, though the USP's standards are also recognized and used in more than 130 countries world-wide. Those products and ingredients that pass all of the USP verification requirements may be marketed with the term “USP Verified” on them. For water, the USP has set production purity standards for two basic types of water: (1) purified water; and (2) water that is suitable for injection. In order to produce water that is suitable for injection, the water that is first fed into a USP water testing or purification system must already be deemed potable, or of sufficient quality to serve as drinking water, by complying with standards set for drinking water by one or more of the known standard setting bodies, such as the U.S. Environmental Protection Agency. This potable water is then treated further to meet the specifications set forth by the USP for USP Verified purified water and/or USP Verified water that is suitable for injection.
Historically, USP purified water systems have been of two types, those for the production of USP Verified purified water which typically consist of pretreatment, reverse osmosis and/or deionization subsystems, and those for USP Verified water this is suitable for injection systems which typically consist of pretreatment and distillation subsystems. Pretreatment, in either of these purification systems, typically consists of multimedia filtration, carbon filtration, and then water softening. The multimedia filtration portion of the pretreatment is usually a mixture of sand and anthracite, a high carbon count mineral coal, of varying particle sizes. The media resides in a cylindrical pressure vessel and water is treated in the multimedia filtration portion of pretreatment by passing it through the cylindrical pressure vessel under pressure. Periodically, the direction of the flow is reversed through the vessel to purge particulate matter that has accumulated in the media. Carbon filtration is applied in a similar manner with carbon granules loaded into a cylindrical pressure vessel. The carbon may be used to remove residual chlorine that is typically present in the drinking water that feeds into the USP water system. In a typical water softener, there are resin beads that are loaded into a vessel and water is passed through the vessel, in contact with the beads. In addition to periodic backwashing, these beads must be periodically regenerated by exposing them to concentrated salt water. In systems using standard deionization, there are resin beads in vessels that are regenerated with caustic and acid. In all of these treatments utilizing vessels filled with granules or beads (i.e., media), there is a strong possibility of organism growth in the vessels. This is due to the many existing sites within the media for organisms to lodge and grow and due to the low velocities of the water pushed through the vessels. In those vessels that utilize carbon, the carbon itself actually leads to organism growth by removing residual disinfectant from the water that would otherwise slow or prevent organism growth. Furthermore, the organic compounds removed from the water by the media provide a food source for organisms, thereby contributing to the overall level of organismal contamination.
Several procedures and systems have been developed to sanitize media filters. To date, the most successful of these systems have been those that utilize hot water sanitization, however these systems are quite expensive to construct and are typically accompanied by large energy costs. Another sanitizing system was designed by Heiss in 1999; this system was not patented, but has been in use continuously since 2000. This system includes the following steps in the following order: ultrafiltration, water softening, ultraviolet dechlorination, single pass reverse osmosis, ultraviolet treatment for the destruction of total organic carbon, membrane degasification, electrodeionization, and finally another step of ultrafiltration. U.S. Pat. No. 6,328,896 to Atnoor et al. describes the use of ultraviolet dechlorination in low doses in conjunction with a water softener. U.S. Pat. No. 6,398,965 to Arba et al. describes a method of using pH adjustment to modify chloramines in association with softening and electrodeionization. U.S. Pat. No. 6,679,988 to Gsell describes use of ultrafiltration and ultraviolet dechlorination with softener in advance of treatment with a still or reverse osmosis. U.S. Pat. No. 6,949,192 to Gsell is a continuation of U.S. Pat. No. 6,799,988 and contains the same disclosure.
All of the aforementioned systems that incorporate ultrafiltration and ultraviolet dechlorination also include the use of water softeners and/or media filtration. Water softeners are included in these systems for three principal reasons: to prevent scaling in reverse osmosis systems, to prevent scaling in electrodeionization systems, and/or to prevent scaling in high intensity ultraviolet lights. In each of these systems, organism growth and contamination is a common problem that must be overcome, often with great time and expense. The present inventors have traced the primary source of organism growth and contamination in these systems to the water softener or to the media filtration systems. Therefore, the use of a water softener in these systems provides a location for organismal contamination to occur.